Consolidated Condensed Statements Of Changes In Stockholders' Equity (USD $) In Thousands, unless otherwise specified	Preferred Stock [Member]	Common Stock [Member]	Retained Earnings [Member]	Treasury Stock At Cost [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Total
Balance at Dec. 31, 2010	$ 97,290	$ 305,677	$ 406,342	$ (77,733)	$ (1,868)
Net Income			22,196			22,196
Other comprehensive income (loss), net of tax:
Unrealized net holding gain (loss) on cash flow hedge, net of income taxes					133	133
Unrealized net holding gain (loss) on securities available-for-sale, net of income tax benefit					(6,371)	(6,371)
Cash dividends on common stock at $0.94 per share			(14,475)
Cash payment for fractional shares in dividend reinvestment plan		(1)
Accretion of discount on preferred stock	214		(214)
Preferred stock dividends			(1,250)
Balance at Mar. 31, 2011	97,504	305,676	412,599	(77,733)	(8,106)
Balance at Dec. 31, 2011	98,146	305,499	424,557	(77,007)	(8,831)	742,364
Net Income			31,475			31,475
Other comprehensive income (loss), net of tax:
Change in pension plan assets and benefit obligations, net of income taxes					412	(412)
Unrealized net holding gain (loss) on cash flow hedge, net of income taxes					113	113
Unrealized net holding gain (loss) on securities available-for-sale, net of income tax benefit					(2,202)	(2,202)
Cash dividends on common stock at $0.94 per share			(14,481)
Cash payment for fractional shares in dividend reinvestment plan		(1)
Accretion of discount on preferred stock	226		(227)
Preferred stock dividends			(1,250)
Balance at Mar. 31, 2012	$ 98,372	$ 305,498	$ 440,074	$ (77,007)	$ (10,508)	$ 756,429